1. Field of the Invention
The present invention relates to stereo systems and, in particular, to a dual-tweeter loudspeaker.
2. Description of the Related Art
Traditionally, stereo dual-tweeter, in-ceiling loudspeakers have been designed and manufactured with two tweeters positioned side-by-side mounted on a post or on a bridge. These traditional speakers may also include a woofer. In both the post and bridge configurations, the tweeters are located over the center of the woofer voice coil and positioned so that the tweeters do not impair the movement of the woofer cone, which can result in dips and peaks in the frequency response. Occasionally, the tweeters will be angled outward in an attempt to improve the stereo imaging effect.
In some designs, the woofer uses a dual voice coil that is wired to terminals that accept signals from both the left and right amplifier channels. When the two signals are connected to the dual voice coil, they are mutually combined and the signals are converted to mechanical energy to produce sound from the woofer. Low frequency energy, primarily because of the long wavelengths, is difficult to localize. Therefore, a stereo effect is perceived from these low frequencies.
Monaural refers to a system where the audio signals are mixed together and routed through a single audio channel. Monaural systems can have multiple loudspeakers, and even multiple widely separated loudspeakers. The stereo signal contains arrival time and phase information that replicates or simulates directional cues found in the original performance. True stereophonic sound systems have two independent audio signal channels, and the signals that are reproduced by the system have a specific level and phase relationship to each other. The desired result when the source information is played back through a loudspeaker system is a reproduction of the original live performance.
A stereo system should also have equal coverage of both the left and right channels, at essentially equal levels. With proper positioning of the loudspeakers, output level and signal arrival time differences between the two loudspeakers are minimal, thus preserving the stereo image and localization characteristics of the original performance, but only within a certain range. Outside that range, the image collapses and only one of the channels can be heard.
Other characteristics that are important when replicating a stereo image from two loudspeakers include uniform coverage over the entire listening area, and a minimal level of phase response difference between the two speakers for each channel's coverage over the listening area.
Therefore, there exists a need for an improved stereo dual-tweeter loudspeaker and particularly for a dual-tweeter loudspeaker which improves the stereo imaging of the speaker system.